Activate Ashnod's Altar by sacrificing another creature, adding {C}{C}.
When the creature dies, Extractor Demon triggers, causing you to mill two cards if your graveyard is empty, or causing an opponent to mill two cards otherwise.
If your library is empty, activate Barkform Harvester by paying {2}, putting a card from your graveyard onto the bottom of your library.
Tormod triggers, creating a 2/2 Zombie creature token.
Repeat.

Infinite creature ETB

Infinite creature sacrifice triggers

Infinite death triggers

Infinite mill

Infinite self-mill

Near-infinite colorless mana

Infinite creature LTB

Tormod, the Desecrator

Extractor Demon

Ashnod's Altar

Barkform Harvester

Activate Ashnod's Altar by sacrificing another creature, adding {C}{C}.
When the creature dies, Extractor Demon triggers, causing you to mill two cards if your graveyard is empty, or causing an opponent to mill two cards otherwise.
If your library is empty, activate Sundering Archaic by paying {2}, putting a card from your graveyard onto the bottom of your library.
Quintorius triggers, creating a 3/2 Spirit creature token.
Repeat.

Quintorius, Field Historian

Sundering Archaic

Activate Ashnod's Altar by sacrificing another creature, adding {C}{C}.
When the creature dies, Extractor Demon triggers, causing you to mill two cards if your graveyard is empty, or causing an opponent to mill two cards otherwise.
If your library is empty, activate Sundering Archaic by paying {2}, putting a card from your graveyard onto the bottom of your library.
Teval triggers, creating a 2/2 Zombie Druid creature token.
Repeat.

Teval, the Balanced Scale

Combos with "Extractor Demon"